Over at the Washington Examiner, Michael Barone highlights a curious pattern in America’s biggest blue cities: Hardly anyone is turning out to vote.

Los Angeles is not unique for low turnout in mayoral elections in very large cities. When Mayor Bill de Blasio was elected Mayor of New York in November 2013, turnout was the lowest since 1929. In an initial primary in March 2015 Chicago Mayor Rahm Emanuel received 218,217 votes—far below the 708,222 votes received by Mayor Richard J. Daley in 1955, a number he put on his license plates ever after. Chicago’s population today is lower than it was in the 1950s, but New York’s population is the highest ever, 1.5 million more than it was in 1929.

Declining voter turnout has tracked the consolidation of Democratic power in big cities. Married middle-class homeowners, who reliably show up at the ballot box (and tend to lean right), have increasingly left for the suburbs. Blue cities like Los Angeles are highly unequal, with small wealthy populations that tend to vote Democratic because of social issues, and large impoverished (often minority or immigrant) populations that are loyal to the Democratic Party but have lower turnout rates overall.

Unionized public employees are one of the only major middle-class constituencies left in many big blue cities. And while large groups of voters don’t feel like they have a stake in city politics, public employees (whose salaries and pensions are at stake) remain highly engaged. Public unions today wield far more influence in city politics than they did in the days of lower turnout and more competitive elections. In other words, a single interest group is accumulating increasing power to direct city politics even as demographic changes lead more and more voters to withdraw from the process altogether.

Needless to say, this is not a sign of a healthy political system. Read Barone’s whole piece to learn more about how we got here.